The following discussion is intended to facilitate the understanding of the invention, but is not intended nor admitted to be prior art to the invention.
A. Atherosclerosis
Atherosclerosis is a complex disease that is characterized by cholesterol deposition and monocyte infiltration into the subendothelial space, resulting in foam cell formation. Cardiovascular disease (mainly atherosclerosis) accounts for 35% of all deaths in the U.S.A. and similar Western countries. The monocyte/macrophage plays key roles both in the initiation and progression of atherosclerosis; for example, hypercholesterolemic mice become extremely resistant to atherosclerosis if they are bred to macrophage-deficient mice [Smith et al, PNAS (1995) 92:8264-8268].
ATP-binding cassette transporter 1 (ABCA1) controls apoAI-mediated cholesterol efflux from macrophages. Expression of ABCA1 is induced during monocyte differentiation into macrophages. ABCA1 protein is dramatically decreased in human atheroma in comparison to nonlesional tissue [Forcheron et al, Arterioscler Thromb Vasc Biol (2005) 25:1711-1717]. Inactivation of ABCA1 in macrophages markedly increases atherosclerosis and foam cell accumulation in ApoE−/− mice [Aiello et al, Arterioscler Thromb Vasc Biol (2002) 22:630-637]. ABCA1 upregulation in macrophages inhibits the progression of atherosclerotic lesions [Van Eck et al, Arterioscler Thromb Vasc Biol. (2006) 26:929-934].
Monocyte chemoattractant protein (MCP-1) is a key mediator of monocyte trafficking. In situ hybridization carried out on atherosclerotic human arteries detected MCP-1 mRNA macrophage-rich regions of atherosclerotic lesions but not in sublesional medial smooth muscle cells or in normal arteries [Yla-Herttuala et al, PNAS (1991) 88:5252-5256; Lutgens et al, Circulation (2005) 111:3443-3452]. MOP-1 expression by macrophages increases the progression of atherosclerosis by increasing both macrophage numbers and oxidized lipid accumulation [Aiello et al, Arterioscler Thromb Vasc Biol (1999) 19:1518-1525]. Use of knockout mice has implicated MCP-1 in attracting macrophage recruitment in atherosclerosis. Atherosclerosis is essentially abolished in MCP-1−/− mice indicating that MCP-1 is absolutely required for atherosclerosis from its earliest stages [Gu et al, Mol Cell (1998) 2:275-281]. Using a dominant-negative mutant of MCP-1, it has been shown that vascular inflammation mediated by MCP-1 has a central role in the development of atherosclerosis, and plaque destabilization, leading to acute myocardial ischemia [Egashira, Hypertension (2003) 41:834-841].
Conditions related to expression of MCP-1 in monocytes/macrophages additional to atherosclerosis and atherosclerotic disease include, but are not limited to, rheumatoid arthritis [see, e.g., Koch et al, J Clin Invest (1992) 90:772-779; Dawson et al, Expert Opin Ther Targets (2003) 7:35-48].
An agent that decreases expression of MCP-1 or increases expression of ABCA1 is useful in the treatment of atherosclerosis and atherosclerotic disease, and an agent which is a small molecule is further advantageous.
B. GPR84
GPR84 is a GPCR asserted to be selectively expressed in granulocytes [Yousefi et al., J Leukoc Biol (2001) 69:1045-1052]. GPR84 has been conjectured to have a role in regulating early IL-4 gene expression in activated T cells [Venkataraman et al, Immunol Lett (2005) 101:144-153].
C. G Protein-Coupled Receptors
Although a number of receptor classes exist in humans, by far the most abundant and therapeutically relevant is represented by the G protein-coupled receptor (GPCR) class. It is estimated that there are some 30,000-40,000 genes within the human genome, and of these, approximately 2% are estimated to code for GPCRs.
GPCRs represent an important area for the development of pharmaceutical products: from approximately 20 of the 100 known GPCRs, approximately 60% of all prescription pharmaceuticals have been developed. For example, in 1999, of the top 100 brand name prescription drugs, the following drugs interact with GPCRs (the primary diseases and/or disorders treated related to the drug is indicated in parentheses):
CLARITIN ® (allergies)PROZAC ® (depression)VASOTEC ® (hypertension)PAXIL ® (depression)ZOLOFT ® (depression)ZYPREXA ®(psychotic disorder)COZZAR ® (hypertension)IMITREX ® (migraine)ZANTAC ® (reflux)PROPULSID ® (reflux disease)RISPERDAL ® (schizophrenia)SEREVENT ® (asthma)PEPCID ® (reflux)GASTER ® (ulcers)ATROVENT ® (bronchospasm)EFFEXOR ® (depression)DEPAKOTE ® (epilepsy)CARDURA ®(prostatic hypertrophy)ALLEGRA ® (allergies)LUPRON ® (prostate cancer)ZOLADEX ® (prostate cancer)DIPRIVAN ® (anesthesia)BUSPAR ® (anxiety)VENTOLIN ® (bronchospasm)HYTRIN ® (hypertension)WELLBUTRIN ® (depression)ZYRTEC ® (rhinitis)PLAVIX ® (MI/stroke)TOPROL-XL ® (hypertension)TENORMIN ® (angina)XALATAN ® (glaucoma)SINGULAIR ® (asthma)DIOVAN ® (hypertension)HARNAL ® (prostatic hyperplasia)(Med Ad News 1999 Data).
GPCRs share a common structural motif, having seven sequences of between 22 to 24 hydrophobic amino acids that form seven alpha helices, each of which spans the membrane (each span is identified by number, i.e., transmembrane-1 (TM-1), transmembrane-2 (TM-2), etc.). The transmembrane helices are joined by strands of amino acids between transmembrane-2 and transmembrane-3, transmembrane-4 and transmembrane-5, and transmembrane-6 and transmembrane-7 on the exterior, or “extracellular” side, of the cell membrane (these are referred to as “extracellular” regions 1, 2 and 3 (EC-1, EC-2 and EC-3), respectively). The transmembrane helices are also joined by strands of amino acids between transmembrane-1 and transmembrane-2, transmembrane-3 and transmembrane-4, and transmembrane-5 and transmembrane-6 on the interior, or “intracellular” side, of the cell membrane (these are referred to as “intracellular” regions 1, 2 and 3 (IC-1, IC-2 and IC-3), respectively). The “carboxy” (“C”) terminus of the receptor lies in the intracellular space within the cell, and the “amino” (“N”) terminus of the receptor lies in the extracellular space outside of the cell.
Generally, when a ligand binds with the receptor (often referred to as “activation” of the receptor), there is a change in the conformation of the receptor that facilitates coupling between the intracellular region and an intracellular “G-protein.” It has been reported that GPCRs are “promiscuous” with respect to G proteins, i.e., that a GPCR can interact with more than one G protein. See, Kenakin, T., 43 Life Sciences 1095 (1988). Although other G proteins exist, currently, Gq, Gs, Gi, Gz and Go are G proteins that have been identified. Ligand-activated GPCR coupling with the G-protein initiates a signaling cascade process (referred to as “signal transduction”). Under normal conditions, signal transduction ultimately results in cellular activation or cellular inhibition. Although not wishing to be bound to theory, it is thought that the IC-3 loop as well as the carboxy terminus of the receptor interact with the G protein.
Gs-coupled GPCRs elevate-intracellular cAMP levels. GPCRs coupled to Gi, Go, or Gz lower intracellular cAMP levels. Gq-coupled GPCRs elevate intracellular IP3 and Ca2+ levels.
There are also promiscuous G proteins, which appear to couple several classes of GPCRs to the phospholipase C pathway, such as G15 or G16 [Offermanns & Simon, J Biol Chem (1995) 270:15175-80], or chimeric G proteins designed to couple a large number of different GPCRs to the same pathway, e.g. phospholipase C [Milligan & Rees, Trends in Pharmaceutical Sciences (1999) 20:118-24]. A GPCR coupled to the phospholipase C pathway elevates intracellular IP3 and Ca2+ levels.
Under physiological conditions, GPCRs exist in the cell membrane in equilibrium between two different conformations: an “inactive” state and an “active” state. A receptor in an inactive state is unable to link to the intracellular signaling transduction pathway to initiate signal transduction leading to a biological response. Changing the receptor conformation to the active state allows linkage to the transduction pathway (via the G-protein) and produces a biological response.
A receptor may be stabilized in an active state by a ligand or a compound such as a drug. Recent discoveries, including but not exclusively limited to modifications to the amino acid sequence of the receptor, provide means other than ligands or drugs to promote and stabilize the receptor in the active state conformation. These means effectively stabilize the receptor in an active state by simulating the effect of a ligand binding to the receptor. Stabilization by such ligand-independent means is termed “constitutive receptor activation.”